1. Field of the Invention
The present invention relates to a combustion plate for use in a totally aerated combustion burner (or a fully primary aerated burner) which is disposed in a heat source equipment mainly for supplying hot water or for heating a residential space, in which a ceramic plate body has formed therein a multiplicity of flame holes (burner holes) so as to eject a premixed gas.
2. Description of the Related Art
As this kind of combustion plate, there is known one in which non-flame-hole portions (i.e., portions having no flame holes) are formed on the plate body in a lattice shape, and in which each of the regions of the plate body enclosed by the non-flame-hole portions is made to be a collective flame-hole portion having formed therein in a crowded manner a plurality of flame holes (see, for example, Patent Document 1). According to this arrangement, the premixed gases that are ejected through flame holes on the periphery of the collective flame-hole portions adjacent to the non-flame-hole portions partly recirculate in a manner to swirl above the non-flame-hole portions. Then, the premixed gases that recirculate back from the flame holes on the periphery of the collective flame-hole portions that are positioned on both sides of the non-flame-hole portions interfere with each other. As a result, there will be formed, above the non-flame-hole portions, stable flames that are hard to be lifted off, thereby obtaining flame holding (stabilizing) effect.
Conventionally, a plurality of flame holes on the periphery of one of the collective flame-hole portions and a plurality of flame holes on the periphery of the other of the collective flame-hole portions lie face to face to each other along both sides, in the width direction, of the non-flame-hole portions, each of the flame holes on the respective periphery forming a pair. In this arrangement, the premixed gas that recirculates from the flame hole that makes one of the pair will get interfered with the premixed gas that recirculates from the other of the pair, above the non-flame-hole portions.
However, according to this arrangement, the following has been found out, i.e., if flame lifting occurs at part of the flame holes on the periphery of the collective flame-hole portions, starting with that point as an origin, the flames from the other flame holes on the periphery of the collective flame portions are likely to be lifted. In particular, in case the excess air ratio (amount of primary air/stoichiometric air amount) of the premixed gas is made higher, flame lifting is likely to occur in the flame holes on the periphery of the collective flame-hole portions. Caused by the above occurrence, there is a case in which flame lifting occurs in the entire collective flame-hole portions.